Spark plug



P. J. DONAVAN.

SPARK PLUG.

APPLICATION FILED JAN. 20. I920.-

' Patented June Paul L]. Drjnavafi.

UNITED, STATES PATENT OFFICE.

PAUL J. DONAVAN, OF DENVER, COLORADO.

' SPARK PLUG.

Specification of Letters Patent. lPatented June 6, 1922.

. Application filed January 20 1920. Serial No. 852,837.

To all whom it may concern."

Be it known that I, PAUL J. DoNAvAN, a

citizen of the United States, residing at the city and county ott D'enver'and' State of Colorado, have invented certain new and useful Improvements in Spark Plugs; and I do declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in'the artto which it appertains' to ,make and use the same, reference being bad to the accompanying drawings, and to the characters of refa wrench in manipulating the nut which" holds the parts of the plug in the assembled relation or in securing the elcctricalbon ductor to the plug. f

My further object is to protect the porcelain or insulating member so far as possible from unequal heating. It is well known that in spark plugs of ordinary construction the porcelain member is so'exposed that it is easily broken in case a wrench slips while assembling the parts of the plug, or when a tool oi": this character is otherwise used in connection therewith. It is also well known that the porcelain member of the ordinary spark plug is so arranged that a part of it is exposed to the intense heat of the combustion chamber, while the other part is lo cated outside of the cylinder and is entirely unprotected from atmospheric temperature, thus exposing the porcelain member to un equal temperature conditions, which. often results in cracking.

My, improvement consists in shortening the porcelain, whereby the upwardly projecting neck of small diameter is done away with. and the upperportion of the plug made relatively large, and its exposed portion rounded and covered by a washer composed of fiber or other suitable material. The bushing nut, which is screwed into the metal body portion of the'plug directly engages this fiberwasher, and when properly adjusted holds the parts of the plug securely in the assembled relation. Furthermore, the stem of the plug is divided, the main portion being securely mounted in the porcelain and carry surface of the insulating member".

ing a sleeve with, which the upper portion,

which extends beyond the porcelain, is detachablyconnected. By virtue of thisconstruction, there is no danger of loosening the stem from. the porcelainby tightening the nut which holds the electrical conductor in place, since while so doing there is no twisting strain on the body of the stem, or the part whichis securely connected with the porcelain or insulating member.

Having briefly outlined my improvement,

I will proceed todescribe the same in detail, reference being made to the accompanying drawing, in which is "illustrated an embodiy ment thereof. In this drawing;

Fig. l is an elevation of my improved I spark plug. i y

' Fig. 2 is a vertical longitudinal section'ot thesame.

Fig. 3 is a similarview, showing the upper portion of the stem detached from the porcelainmember and from the cooperating stem portion. v y

The samereference characters indlcate the same parts 1n all the views.

Let thenumeral 5 designate the metal. body of theplug, whose lower portion is threaded, as shown at 6, for connection with the cylinder of the engine. The insulating member 7 has a rounded or convex upper surface, which is covered by a washer 8. preferablycomposed of fiber and engaged by a bushing nut 9, which is exteriorly threaded to cooperate with the interior threads of the metal body part 5 of the plug, the bushing nut being interio'rly curved to correspond with the curvature of the outer As the upper portion of the last named member is relatively thick or heavy and its exposed portion curved. and protected by the washer 8, there is practically no danger of breakage by the slipping of a wrench, either when connecting the plug with the engine or while screwing the bushing nut into place, or when tightening the nut 10, which connects the electrical conductor with the stem.

The upper central portion of the porcelain member 7 is provided with a recess 12, surrounded by a sleeve 13, which is cast or moulded in the porcelain member, the lower portion of the sleeve being further permanently connected with the body 14 of the stem, which extends downwardly through an opening in the porcelain, its lower extremity constituting an, electrode which cooperates with a second electrode 15, which is connected with the metal body member 5. The sleeve 13 is exteriorly beaded, as shown at 16, to form an interior circumferential groove adapted to receive an exterior head 17 formed on the detachable part 18 of the stem whose lower portion is slotted, as shown at 19, to permit slight contraction while inserting the member 18 in the recess 12. As soon as this member is pushed into the recess 12 to its limit of movement, the bead 17 will spring outwardly into the in terior groove of the sleeve 13, whereby the two stem parts are interlocked andv constitute for all practical purposes an integral device.

It will be understood that when in use an electrical conductor (not shown) is coirnected with the part 18 of the stem, between a collar 20 formed on the said part, and a top nut 10, which is interiorly threaded'to cooperate with the threaded part 22. It will be understood that whentightening the nut 10 there is no twisting strain on the body part 1 1 of the stem, which would have a tendency to loosen the stem or breakit away from the porcelain .member with which. it must be securely connected. It will thus be understood that the part 18' of the stem is readily attachable and detachable from its cooperating stem member and from the insulating or porcelain part 7. Suitable gaskets 23 are arranged between the inclined shoulders on the porcelain member 7, and 0p posing shoulders on the metal body part 5 of the plug, thus giving a cushioning effect while at the same time holding the elements in suitable cooperative relation.

Attention is also called to the fact that by reason of the divided stem and the resilient inner portion of the member 18, a considerable degree of flexibility is provided for without in any way interfering with the function of the stem as an electrical conductor. By virtue of this feature liability to breakage of the parts, or disturbance of the proper cooperative relation between the elements of the stem is to a large extent obviated or minimized. The stem member lei, as well as the sleeve 13, is cast permanently in the porcelain member.

I claim:

1. A spark plug, whose insulating member is convexly curved exteriorlyw a fiber washer covering said curved part of said member, and a bushing nut threaded into the metal body and concaved to conform to the curvature of the adjacent part of the insulating member, and arranged to engage said washer.

2. In a spark plug, a body, an insuli'itinq porcelain therein, a bushing threaded into i the body to retain the porcelain and through which the porcelain is exposed, said porcelain being short so that its top is approximately flush with the top of the bushing, whereby the porcelain is protected from injury by blows, and a protecting washer on the upper portion of the porcelain for further protection thereof.

In testimony whereof I aflix my signature.

PAUL J. DONA VAN. 

